Works of production belonging to fields of electronic instrument or precision processing industry are carried out in a clean room. A rubber gloves which is used by operators working in clean room is prepared by forming materials under the presence of sulfur as a crosslinking agent, or zinc oxide and sulfur compound as a vulcanization accelerator. Sometimes, a vulcanization accelerator which contains sulfur compound can be used. When operator uses a rubber gloves containing sulfur and vulcanization accelerator, sometimes, the operator causes IV type hypersensitivity and becomes to cause casualty of health. Unfortunately, up to the present time, development of gloves by use of rubber which does not use sulfur or sulfur composition which are crosslinking agent and vulcanization accelerator has been considered to be difficult.
By use of said conventional gloves, the users are troubled by casualty of IV type hypersensitivity. Further, in fields of semi-conductor or precision processing, dust or impurities contacts with products and is accumulated, and affects to properties of the products. And this phenomenon is considered as undesirable phenomenon. Regarding a gloves for clean room use, physical properties such as easy elongation and strong resistance against breaking are required. Further, regarding used gloves, recycling is required, and it becomes necessary that the gloves are made of materials which are easier recycling.
U.S. Pat. No. 5,014,362 (Patent Document 1) discloses a crosslinking method of carboxylic nitrile rubber using zinc oxide and sulfur. Typical carboxylic nitrile rubber is formed by segment consisting of acrylonitrile, butadiene and organic acid formed by various mixing ratio. By use of sulfur and a vulcanization accelerator, it becomes possible to form crosslinking by covalent bond in sub segment of butadiene. Further, in a part of carboxylated acrylonitrile (organic acid) ionic bond can be formed by using metal oxide such as zinc oxide or other metal salts. Ionic crosslinking is carried out by zinc ion and use crosslinking by sulfur too. Further, as the method to prepare NBR gloves, U.S. Pat. No. 6,673,871 publication (Patent Document 1), regarding elastomeric product such as gloves, the method to use metal oxide such as zinc oxide as a crosslinking agent by not using crosslinking agent or a vulcanizing agent containing sulfur is disclosed. However, in general, it is considered that only use of zinc oxide is not sufficient.
In the specification of U.S. Pat. No. 7,005,478 publication (Patent Document 2) there is follows disclosure. That is, at the preparation of a product consisting of elastomer, react elastomer possessing a carboxyl group with (a) carboxylic acid or derivatives thereof, (b) compound containing bivalent or trivalent metal and (c) amine or amino compound in (d) condition to contain a neutralizing agent which neutralizes at least a part of carboxylic acid group in said base polymer. At the reaction, a vulcanizing accelerator, thiuram and carbamate are not used. As a base polymer, natural latex rubber, synthetic latex polymer (e.g. acrylonitrile), butadiene rubber such as synthetic butadiene rubber or carboxylic butadiene rubber are mentioned as an example, however MMA is not contained. Or, does not use carboxylated acrylonitrile. In this method, said (c) amine or amino compound is essential component. Amine group or amino group reacts with carboxylic acid derivatives and forms complex with bivalent or trivalent metal. By using complex forming reaction, stabilization becomes difficult and as the result, it is pointed out that a stabilized product is difficult to obtain.
In Non Patent Document 1 (Andrew Kells and Bob Grobes “Cross-linking in carboxylated nitrile rubber dipped film” LATEX 24-25, January 2006 Frankfurt, Germany) reports that a latex, whose tensile strength is improved, is obtained by using tetramethylthiuram (TMTD), 2,2′-dithio-bis(benzothiazole) (MBTS), N-cyclohexylbenzothiazole-sulfinicamide (CBS), zinc diethylthio carbamate (ZDEC) and necessary additives consisting of zinc oxide with small amount of sulfur. This report shows that carboxylic nitrile latex gloves having excellent durability cannot be obtained without use sulfur or a vulcanizing accelerator based on sulfur.
A method to prepare a gloves from self crosslinking material is investigated, while, action of self crosslinking method which is necessary for preparation of desired gloves is not technically explained in the report. It is understood that sufficient results are not obtained regarding technical explanation of self crosslinking latex.
In Non Patent Document 2 (Dr. SorenBuzs “Tailored synthetic dipping lattices: New approach for thin soft and strong gloves and for accelerator-free dipping” LATEX 23-24, January 2008, Madrid, Spain) following two crosslinking methods are disclosed. That is, direct crosslinking method of NBR latex by functional reactive group (R) instead of conventional sulfur crosslinking, and crosslinking method of NBR latex by ionic bond formed between carboxyl group of NBR latex by zinc oxide. And, the document reports that this method is promising as a future technique. Unfortunately, there is no specific explanation about functional group which acts in covalent bond. And is not succeeded to make clear the concrete method for forming.
In Nichias technical information (Vol 5, 2000, No. 321), combination of epoxidated natural rubber and carboxylic NBR is used for self crosslinking.
Regarding said point, the applicant of this application has also filed another application on same day of this application.